Tacked to my wall is a lithograph of the famous Gilbert Stuart portrait of George Washington. For many years, it graced my mother's one-room schoolhouse in Lime Rock, N.Y. Antiquarian relic or enduringly relevant image? The same question may be asked of the "little red schoolhouse" itself, whose reality and legend are the subject of "Small Wonder." Jonathan Zimmerman, a professor at New York University, sets out to tell "how -- and why -- the little red schoolhouse became an American icon." Mr. Zimmerman proves a thoughtful and entertaining teacher. First, the chromatic debunking: One-room schools were often white and...